KR20120057578A - Aluminum base material, metal substrate having insulating layer employing the aluminum base material, semiconductor element, and solar battery - Google Patents

Abstract

 Provided are a metal substrate which can be manufactured by a simple process, exhibits heat resistance during a semiconductor process, is excellent in voltage resistance, and has a low leakage current, and an Al substrate for realizing the metal substrate. A metal substrate having an insulating layer is formed by subjecting at least one surface of the Al substrate to anode oxidation. The Al substrate contains only precipitated particles of a material which are anodized by anode oxidation as precipitated particles in an Al matrix.

Description

Aluminum substrate, metal substrate, semiconductor device, and solar cell having an insulating layer using the aluminum substrate {ALUMINUM BASE MATERIAL, METAL SUBSTRATE HAVING INSULATING LAYER EMPLOYING THE ALUMINUM BASE MATERIAL, SEMICONDUCTOR ELEMENT, AND SOLAR BATTERY}

The present invention relates to an Al base material for forming a metal substrate having an insulating layer for a semiconductor element whose anode layer is an insulating layer, a metal substrate having the insulating layer, a semiconductor element, and a solar cell.

BACKGROUND OF THE INVENTION In forming semiconductor devices such as solar cells and TFTs (thin film transistors), flexibility and weight reduction have recently been advanced. The flexible device can be used for various uses such as an electronic paper and a flexible display.

As a substrate of a semiconductor element, a glass substrate has been mainly used because heat resistance and the like that the substrate can withstand at a formation temperature of a semiconductor film having excellent insulation and semiconductor device characteristics formed thereon are required. However, the glass substrate is fragile and poor in flexibility. Therefore, it is difficult to form a thin, ultra-light glass substrate.

For this reason, as a board | substrate which is lightweight compared with the conventional glass substrate, excellent in flexibility, and withstands high temperature processing, the board | substrate formed from metals, such as Al and stainless steel with an insulating film, is considered. As described above, the semiconductor circuit and the substrate need to be insulated from each other. The insulating film is required to have low leakage current (high resistance), high withstand voltage, and no breakdown due to the voltage applied during use.

For example, in a CIGS solar cell, the voltage generated by each solar cell is at most 0.65V. However, module circuits in which nearly 100 cells are connected in series on a single substrate are common. In consideration of safety and long-term reliability, an insulation voltage of 500 V or more is required for the insulating film of the metal substrate. In addition, even when dielectric breakdown does not occur, the presence of a leakage current may lower the photoelectric conversion efficiency of the solar cell module.

Japanese Unexamined Patent Publication No. 2001-339081 discloses a CIGS solar cell using a substrate provided with an insulating layer on both sides of a conductive base. However, the substrate of Japanese Unexamined Patent Publication No. 2001-339081 is obtained by forming an oxide film on a metal base by a gas phase method or a liquid phase method. This makes it easy to form pinholes, cracks, and the like in the oxide film. Further, from the point of adhesion, the oxide film is likely to peel off from the metal substrate during semiconductor processing. Due to this drawback, it is difficult to obtain a semiconductor device having good device characteristics.

On the other hand, it has been proposed to use an Al substrate having an anode oxidation treatment on the surface of an Al substrate and having a porous AAO (Anodized Almminum 0xide) film formed on the surface. Such a substrate is composed of an insulating layer formed of an anodized portion and a metal layer (Al layer) formed from an anodized non-anodized portion. Therefore, the adhesion between the insulating layer and the metal layer is good, and a large area substrate can be obtained in a single processing step. However, AAO membranes are porous membranes and therefore their insulation is not high. Therefore, techniques for improving the insulation of AAO films and techniques for compensating for deterioration of device characteristics caused by poor insulation have been proposed (Japanese Unexamined Patent Publication Nos. 2000-049372, 7 (1995) -147416, and 2003-330249). ).

Japanese Unexamined Patent Publication No. 2000-049372 proposes an improvement in device characteristics by increasing light utilization efficiency by forming a non-uniform structure on the surface of a substrate. Japanese Unexamined Patent Publication No. 7 (1995) -147416 discloses a liquid crystal matrix panel in which the surface of an AAO film is coated with a SiN film to improve insulation. In Japanese Unexamined Patent Publication No. 2003-330249, in order to improve insulation, the barrier layer thickness, which is an alumina layer between the bottom of the micropores of the porous portion and the Al base, is thickened by the pore filling method.

In Japanese Unexamined Patent Publication No. 2000-049372, device characteristics are improved by a non-uniform structure formed on a substrate surface. However, the insulation itself does not improve, and there are still problems regarding the breakdown voltage and the leakage current. In addition, the methods proposed in Japanese Unexamined Patent Publication Nos. 7 (1995) -147416 and 2003-330249 require a further process after AAO film formation.

This invention is made | formed in view of the said situation. It is an object of the present invention to provide a metal substrate having an insulating layer which can be manufactured in a simple process, has heat resistance during semiconductor processing, is excellent in voltage resistance, and has a low leakage current. Another object of the present invention is to provide an Al substrate for realizing a metal substrate.

Still another object of the present invention is to provide a semiconductor device and a solar cell using a metal substrate having an insulating layer.

MEANS TO SOLVE THE PROBLEM This inventor earnestly examined about the factor which lowers the leakage current characteristic and withstand voltage characteristic of the Al substrate (henceforth AAO (Anodized Almminun Oxide) substrate) provided with the anodization film on the surface used as a semiconductor element substrate. As a result of examination of the example, it succeeded in discovering the new design idea of the board | substrate for semiconductor elements excellent in the leakage current characteristic and withstand voltage characteristic. MEANS TO SOLVE THE PROBLEM This inventor invented the semiconductor element which used the board | substrate for semiconductor elements and the semiconductor element board | substrate which implement | achieves the board | substrate for semiconductor elements excellent in the leakage current characteristic and withstand voltage characteristic based on the said novel design idea.

That is, the Al substrate of the present invention is an Al substrate used for a method of forming a metal substrate having an insulating layer for a semiconductor device by performing anode oxidation on at least one surface.

The precipitated particles in the Al matrix are characterized in that only precipitated particles of a substance which can be anode oxidized by anode oxidation are included (may include unavoidable impurities).

Here, the Al substrate containing the precipitated particles may be pure Al, pure Al crystals having a solid solute element of trace inevitable impurities, or an alloy matrix of Al and trace amounts of other metal elements. The content of unavoidable impurity elements and precipitated particles contained in the Al matrix is 10% by weight or less of the Al substrate.

Here, the term “precipitated particles” refers to materials of amorphous and grain form amorphous and different in Al matrix. For example, industrially annealed aluminum contains trace amounts of impurities. As a result of impurities exceeding the solid solute limit, the impurity component and metal particles such as Al intermetallic compounds or metal Si are unevenly distributed to form precipitated particles. Examples of generally known precipitated particles include stable intermetallic compounds such as metal Si, Al ₃ Mg ₂ , Al ₃ Fe, Mg ₂ Si, CuAl _2, and Al ₆ Mn; And metastable intermetallic compounds such as α-AlFeSi and Al ₆ Fe, depending on the refining conditions during heat treatment.

Metal Si in the Al substrate is conductive Si in which a small amount of impurities are dissolved in the Si crystal.

"Contains only precipitated particles of a material that can be oxidized by anodized oxidation" means that all precipitated particles present in the Al substrate are anodized precipitated particles and non-anodized precipitated particles will substantially satisfy the object of the present invention. It also includes a state that exists within the range of possible. Here, the "range that can substantially satisfy the object of the present invention" may be appropriately set according to the particle size of the non-anode precipitated particles or the number of particles per cross-sectional area.

Hereinafter, the precipitated particles of the material which is anodized during the anode oxidation based on Al are referred to as "anodized precipitated particles", and the precipitated particles of the material which are not anodized during the anode oxidation based on Al are referred to as "non-anodized precipitated particles".

In the Al substrate of the present invention, the material to be anodized is preferably an intermetallic compound containing one of Al and Mg.

In the Al substrate of the present invention, it is preferable that metal Si is not substantially contained as precipitated particles in the Al substrate.

Here, when the metal Si precipitated particles are "substantially not included" when the surface of the Al substrate is analyzed by an Electron Probe Micro Analyzer (EPMA), the presence of the metal Si precipitated particles cannot be confirmed. It is said to mean. That is, no precipitated particles below the spatial resolution that can be detected with EPMA are observed, but the amount of metal Si is acceptable. Of course, since the metal Si precipitated particles are preferably not included at all, it is preferable to control the amount of the metal Si to be less than that which can be confirmed by other analysis methods.

Furthermore, if a polishing compound containing Si, such as SiO ₂ and SiC on a substrate, there is a case abrasive it is being hit by the soft Al matrix of the substrate. Thus, the embedded abrasive may be erroneously detected as metal Si. Thus, the substrate can be observed after being immersed in NaOH solution to dissolve the Al surface, distinguishingly removing the embedded abrasive, and cleaning.

The metal substrate having the insulating layer of the present invention is characterized in that an anodized film is formed on at least one surface of the A1 substrate by performing anode oxidation on at least one surface of the Al substrate.

The semiconductor device of the present invention is characterized by including a metal substrate having an insulating layer of the present invention, a semiconductor layer formed on the metal substrate, and at least one pair of electrodes for applying a voltage to the semiconductor layer.

It is preferable that the semiconductor element of this invention is a photoelectric conversion element which has a photoelectric conversion function in which the said semiconductor layer produces an electric current by light absorption. It is preferable that the main component of the said semiconductor layer is a compound semiconductor of at least 1 type chalcopite structure. It is preferable that the said compound semiconductor of the chalcopite structure is at least 1 type compound semiconductor which consists of group Ib element, group IIIb element, and group VIb element. At least one group Ib element may be selected from the group consisting of Cu and Ag, at least one group IIIb element may be selected from the group consisting of Al, Ga, and In, and at least one group VIb element is S, Se And it may be selected from the group consisting of Te.

In the present specification, the "main component" means a component containing 90% by weight or more.

The solar cell of this invention is equipped with the photoelectric conversion semiconductor element of this invention. It is characterized by the above-mentioned.

Japanese Unexamined Patent Publication No. 2002-241992 discloses an anodized aluminum alloy component for a surface treatment device having excellent withstand voltage characteristics that defines the number of bulky intermetallic compounds contained in an anode film per square millimeter. In the invention of this patent document, there is found a correlation between the abnormal discharge generated due to the low withstand voltage characteristics of the components in the surface treatment apparatus for generating the fluorine plasma and the number of bulky intermetallic compounds in the anode film. Thus, the invention of this document defines an upper limit of the number of bulky intermetallic compounds per square millimeter of anodized film.

In the above patent document, the intermetallic compound present in the material and included in the anode film is oxidized only slightly during the anode oxidation treatment, remains substantially in the metal state, dissolved during the anode oxidation treatment, and dissolved into the cavity in the film. Form. There are differences in the breakdown voltage characteristics, but these two factors are described as affecting the breakdown voltage and causing abnormal discharge (paragraph, etc.).

As described above, the electrical characteristics required for the components of the surface treatment apparatus for generating the fluorine plasma are the withstand voltages such that abnormal discharge can be suppressed during the generation of the fluorine plasma. On the other hand, the electrical characteristics required for the substrate for semiconductor elements in the present invention are leakage current characteristics and high reliability withstand voltages that result in good element characteristics.

As described above, the present inventors have found that the insulating property of the barrier layer on the bottom surface of the anode film of the AAO substrate for semiconductor devices is very important for determining the leakage current characteristic and withstand voltage characteristic. That is, it was found that the insulation of the barrier layer greatly influences the leakage current characteristics and withstand voltage characteristics of the AAO substrate for semiconductor elements. It has also been found that the anodized intermetallic compounds present in the anodized film do not form dissolved cavities, but result in a non-uniform porous layer, and the non-uniform porous layer has little effect on the insulation of the anodized film. The details regarding these findings are described later.

In Japanese Unexamined Patent Publication No. 2002-241992, there is no description regarding leakage current characteristics. In addition, description regarding the abundance rate of an intermetallic compound is made with respect to the whole anodized film, and what is most important about insulation of a barrier layer is not carried out in-flight or suggestive. Therefore, the invention of the present application has a configuration that is completely different from the invention described in Japanese Unexamined Patent Publication No. 2002-24l992, and also has a problem and a purpose.

The present invention provides a novel design idea of an Al substrate (AAO substrate) having an anode film on a surface used as a substrate of a semiconductor device having excellent leakage current characteristics and withstand voltage characteristics. According to the present invention, it is possible to obtain a metal substrate having an insulating layer which can be manufactured by a simple process, has heat resistance during semiconductor processing, is excellent in voltage resistance characteristics, and has a low leakage current.

The Al substrate of the present invention contains only precipitated particles of a material which can be anodized by anode oxidation as precipitated particles in an Al matrix. Therefore, when a metal substrate having an insulating layer is formed by performing anode oxidation on the Al substrate, the precipitated particles contained in the anode film during the anode oxidation are only insulator particles obtained by anodization together with the Al substrate. Therefore, the metal substrate which has the insulating layer obtained using the said Al base material does not contain electroconductive precipitated particle which greatly reduces insulation characteristics in the barrier layer of the bottom of the said insulating layer. Therefore, a metal substrate having an insulating layer having a high withstand voltage of the insulating layer and a small leakage current can be realized.

The semiconductor device using the metal substrate having the insulating layer of the present invention is a highly durable semiconductor capable of maximally utilizing the characteristics (photoelectric conversion characteristics, etc.) of the semiconductor device because of its excellent withstand voltage characteristics and leakage current characteristics. .

1 is a graph showing the current-voltage characteristics of an AAO substrate obtained by anodizing a high purity Al substrate (Al-polarity).
2 is an enlarged view of one pore of the porous layer.
It is a schematic sectional drawing which shows the structure of Al board | substrate which concerns on 1st Embodiment of this invention.
FIG. 3B is a schematic cross-sectional view showing the structure of a metal substrate having an insulating layer obtained by anodizing the Al substrate of FIG. 3A.
4A is a schematic cross-sectional view showing the configuration of an Al substrate including metal precipitated particles.
FIG. 4B is a schematic cross-sectional view showing the structure of a metal substrate having an insulating layer obtained by anodizing the Al substrate of FIG. 4A.
5 is a schematic cross-sectional view showing a semiconductor device according to a second embodiment of the present invention.
6 is a graph showing the relationship between the lattice constant and the band gap of the I-III-VI compound semiconductor.
7 is an electron micrograph of a metal substrate having an insulating layer having anodized precipitated particles of Example 2. FIG.
8A is a graph showing the overcurrent characteristic of Example 1. FIG.
8B is a graph showing the overcurrent characteristic of Example 2. FIG.
8C is a graph showing the overcurrent characteristic of Comparative Example 1. FIG.

[Metal substrate having Al substrate and insulating layer]

The present invention relates to an Al substrate having an anodized film obtained by partially anodizing the surface of an Al substrate used as a metal substrate having an insulating layer for semiconductor elements. Moreover, this invention relates to the industrial Al base material which can manufacture Al substrate which has an anode film. The present inventors earnestly examined the factor which degrades the insulation of Al board | substrate (henceforth AAO board | substrate) which has an anode film. As a result, it was found that the insulation of the barrier layer at the bottom of the anode film of the AAO substrate was important. In addition, it was found that the insulation property of the AAO substrate is greatly reduced due to the presence of non-anodized precipitated particles which remain as metals without being anode oxidized during anode oxidation among the unavoidable impurities contained in the Al substrate.

First, in order to remove the influence of unavoidable impurities, the inventors have used aluminum having a purity of 99.99% or more, such as that used for high purity JIS1N99, to prepare an AAO substrate. Then, the breakdown voltage characteristic of the AAO substrate was measured. The method for producing the Al substrate is as follows. The solution was prepared using aluminum having a purity of at least 99.99% as used in JIS1N99, and solution heat treatment and filtration were performed to prepare an ingot having a thickness of 500 mm and a width of 1200 mm by the DC casting method. The surface of the ingot was milled to an average thickness of 10 mm by surface miller. Subsequently, isothermal heating was performed at 550 ° C. for about 5 hours. When the temperature was lowered to 400 ° C., the ingot was rolled with a hot rolling mill to form a rolled plate having a thickness of 2.7 mm. Further, the heat treatment was performed at 500 ° C. for 1 hour by an annealing apparatus, and the rolled plate was finished to be 0.24 mm in thickness by cold rolling using a mirror finished roll.

The surface of the Al material was ultrasonically cleaned with ethanol and electropolished with a mixed solution of acetic acid and perchloric acid. Subsequently, electrostatic potential electrolysis was performed on the Al substrate in 0.5 mol / L at 40 V to form an anode film having a thickness of 10 탆 on the surface of the Al substrate.

The leakage current of the obtained AAO substrate was measured by applying a voltage of negative polarity to the Al layer remaining without being anodized. On the anodized surface, a 0.2 mu m thick Au film having a diameter of 5 mm diameter was formed by mask deposition as an electrode. Voltage was applied between the Au electrode and the Al substrate to measure the current voltage characteristics and the dielectric breakdown voltage. Voltage was applied for 1 second in 1OV steps until dielectric breakdown occurred. Here, the leakage current density was a value obtained by dividing the leakage current by the Au electrode area (9.6 mm ² ). The result is shown in FIG.

1 is a graph showing current voltage characteristics. The graph shows that current starts to flow rapidly around 200V, and dielectric breakdown occurs around 400V. That is, high resistance is observed to around 200V, and it is thought that the amount of current based on the unique volume resistance of the barrier layer flows. On the other hand, a large amount of spike-shaped current is observed up to the dielectric breakdown voltage near 200V. This is thought to generate spike currents due to micro shots because local breakdown occurs locally in the electrically weak part of the barrier layer. As the voltage increases, the number of barrier layers in which micro shorts are generated increases, and the amount of micro short currents increases in each micropore, and finally the material itself is destroyed by joule heating, which is a product of leakage current and applied voltage. This causes breakdown of the entire AAO substrate. 1 shows a plurality of current-voltage characteristics which are measurement results obtained for the same AAO substrate using different Au electrodes.

From the above results, it is believed that if local dielectric breakdown starts to occur in the barrier layer, the amount of leakage current suddenly increases and can lead to dielectric breakdown of the entire AAO substrate.

2 is a graph showing an enlarged view of one pore of the multi-light layer in a state where a voltage is applied. Considering the electric circuit, a voltage is applied to a circuit in which the resistance RB of the barrier layer and the resistance RP of the porous layer are connected in series.

In FIG. 1, when the resistance R ¹ is calculated from the inclination of the ohmic region from 0 to 100V, R = 5.1 × 10 ⁸ Ωcm ² . Considering that the thickness of the barrier layer is about 50 nm, the volume resistivity of the barrier layer of the AAO substrate is calculated to be about 10 ¹⁴ Ωcm level. Further, based on the fact that the pore diameter is about 30 nm, the barrier layer resistance RB of each fine pore is calculated to be 10 ²⁰ Ω. The surface resistance of the AAO substrate is 10 ¹⁰ Ω / □ by separate measurement. Based on this value, the surface resistance RP of the inner wall of each micropore in the porous layer is calculated to be 10 ¹² Ω from 30 nmφ × 10 μm. Therefore, in the voltage range where no micro short occurs, the sum of the resistance value of the barrier layer and the resistance value of the porous layer becomes the total resistance. However, since the resistance value of the porous layer is significantly lower than that of the barrier layer, the resistance value of the barrier layer is a true resistance value. On the other hand, when the barrier layer is insulated from breakdown and micro short occurs, the resistance of the barrier layer is substantially zero, and a current flows in accordance with the surface resistance RP of the inner wall of the fine pores.

From the above, the influence of the barrier layer on the insulation related to the leakage current characteristic and the breakdown voltage characteristic of the AAO substrate is large. Therefore, it was confirmed that the insulating property which has a barrier layer as a board | substrate for semiconductor elements is favorable.

Next, the inventors examined the influence of unavoidable impurities on the insulation of the AAO substrate.

For Al substrates, there is a purity grade of Al. In general, JIS 1080 Al, which is used as a wrought industrial Al substrate, has an Al purity of more than 99.8%, and Si and Fe of 0.15% by weight, respectively. JIS 1100 Al has an Al purity of more than 99.0% and Si and Fe allow 0.95% by weight. This unavoidable impurity exists as a solid solute in the Al crystal of the Al matrix and exists as precipitated particles which are elements that exceed the solid solute limit and become metals or intermetallic compounds.

Based on the above findings, the inventors thought that the influence of the presence of these precipitated particles on the insulation of the AAO substrate depends on whether the precipitated particles are anodized, that is, whether or not they can become insulators by anode oxidation. . The inventors have found that the absence of non-anode particles, particularly in and near the barrier layer, is very important for the leakage current characteristics and withstand voltage characteristics of the AAO substrate.

That is, the Al substrate 1 of the first embodiment includes precipitated particles 15 that cannot be dissolved in an Al matrix, and among the impurities contained in the industrial Al substrate, the precipitated particles l 5 are anodes of the Al substrate. It is an intermetallic compound that becomes an oxide by being anode during oxidation (hereinafter, referred to as anodized precipitate particles 15).

When the Al base material 1 shown in FIG. 3A is anodized from the surface 1s, the anode film 11 which consists of an anodeing porous layer 14p, the barrier layer 14b, and the micropore 12; And non-anodeized portion 10 is obtained. The anodized precipitated particles 15 that existed in the Al matrix before the anode oxidation become oxide particles 15a which are anodized together with the Al matrix (see FIG. 3B). As shown in FIG. 3B, when only the said anodized particle 15 exists, the board | substrate which has an insulation layer obtained (porous layer 14p or barrier layer 14b in the anode film 11 in AAO board | substrate 2). No conductive material is present in the anode, and assuming that anodized particles 15 exist at the interface between the porous layer 14p and the barrier layer 14b of the oxide film 11, the same as the Al matrix. Anodization occurs due to an electrochemical mechanism, and therefore it is considered that the barrier layer 15b is present at the interface between the anodized portion 15 'and the non-anodized portion 15' of the anodized particles 15. Therefore, irrespective of the portion where the anodized particles 15 are present, the influence on the insulation of the AAO substrate is very small, as shown in Fig. 8 of the second embodiment, which will be described later. ) And its side toward the barrier layer 14b is porous. Is different from the part that does not exist anode particles 15, a structure is non-uniform, but, in order to simplify the explanation, the non-uniform porous structure are not shown in FIG.

On the other hand, when the Al substrate 1 'shown in Fig. 4A is anodized from the surface 1's, an anode film composed of the anodized porous layer 14'p, the barrier layer 14'b and the fine pores 12'. (11 ') is obtained. The non-anodized precipitated particles 16 present in the Al matrix prior to the anodic oxidation are not anodized and exist as metal particles 16 (16a, 16b, 16c) (see FIG. 4b). As shown in FIG. 4B, the non-anode precipitated particles 16 are not anodized and exist as the metal particles 16, regardless of whether they exist in the porous layer 14'p or the barrier layer l4'b. The metal particles 14 without affecting the insulation of the substrate (AAO substrate) 2 'having the resulting insulating layer. In particular, in the case of the metal particle 16a, electroconductive particle exists over the thickness of the anode film 11 '. Therefore, insulation cannot be obtained and this portion is in a conductive state. In the case of the metal particles 16b, there are many defects in the barrier layer, and the barrier layer exhibits poor insulation. In the case of the metal particle 16c, the adverse influence is estimated to be slight. However, when a micro short occurs between the barrier layer 14 'at the interface with the Al substrate 1' and the metal particles 16c, the leakage current is at these positions compared to the portion where the metal particles 16c do not exist. Becomes large. Referring to FIG. 8 to be described later, a portion of the non-anode particles 16c having a non-uniform porous structure on the side of the non-anode particles 16c facing the barrier layer 14b 'is different. However, for the sake of simplicity, the heterogeneous porous structure is not shown in FIG. 4B.

As described above, there is a difference in the influence exerted by the non-anode oxide precipitated particles 16 on the insulating phase of the AAO substrate 2 'depending on the position. However, inevitable impurities in the entire industrial Al substrate exist randomly. Therefore, the manufacturing method of performing anode oxidation to the point of non-anodized precipitation particle 16 which does not exist in a barrier layer is not realistic. Therefore, it is necessary that the Al substrate 1 contains only the anodized precipitated particles 1, and the non-anode precipitated particles 16 are practically not included.

The material that is anodized during anode oxidation of Al substrates also depends on the electrolyte used. Examples of representative electrolyte materials include "Research Report on the Influence of Intermetallic Compounds on Surface Processability of Aluminum Alloy (Part 1)", Surface Processing Technical Research Group, Research Committee, The Japan Institute of Light Metals, Ed., July 20, Described in 1990. For example, an intermetallic compound containing Al or Mg as the anodized precipitated particles 15 is preferable due to the fact that the intermetallic compound is anodized during Al-based anode oxidation using a common electrolyte solution. It is also known that metal Si is not anodeed by anode oxidation using an aqueous electrolyte solution.

As specified by JIS (Japanese Industrial Standard), it is necessary to use pure 1000 industrial Al or 1000 Al-Mg alloy to aluminize Si, Fe and other unavoidable impurities (intermetallic compound with Al). Or an intermetallic compound with Mg and unavoidable impurities. For example, when the industrial Al has the composition, the heat treatment after rolling is performed at a temperature of 577 ° C. or lower, which is the co-crystallization temperature of Si-Ai, to suppress the precipitation of metal Si, and to precipitate α-AlFeSi which can be anodized. You can.

Metals of JIS 1000 series and 5000 series are listed as examples of industrial Al. However, any Al substrate may be used as long as the precipitate can be anodized simultaneously with the Al matrix. What is important is not the composition or alloy concentration of the Al substrate, but the electrochemical properties of the precipitated particles. In addition, various metallic elements such as Fe, Si, Mn, Cu, Mg, Cr, Zn, Bi, Ni, and Li may be contained in pure high purity Al. However, if the metal components are included in amounts exceeding the solid solute limit, it is important that they precipitate as aluminides (intermetallic compounds with Al).

Since metal Si cannot be anodized, in particular, when Si is not aluminized, it is necessary to remove metal Si from the Al material. Al other than the above which precipitate of metal Si is suppressed and precipitation as alpha-AlFeSi which Si can anodize by performing heating temperature after rolling at the temperature below 577 degreeC (co-crystallization temperature of Si-Al) of precipitation of metal Si is carried out. Known methods for removing the metal Si from are listed below.

Japanese Patent Laid-Open No. 62 (1987) -010315 describes a method for refining aluminum containing impurities by electrolysis. The method can also be applied to remove metal Si and other impurities. However, impurities only from the surface of aluminum are removed, and metal Si in aluminum existing at positions of several micrometers or more from the surface cannot be removed. Thus, this method is not suitable when an anode film having a thickness of about 10 mu m is formed.

Japanese Patent Application Laid-Open No. 1 (1989) -279712 describes a method of using a phenomenon in which Al high-purity portion first solidifies when molten Al or Al alloy is solidified. In this method, molten metal Si is concentrated and removed from the non-solidified molten metal during the final stage of solidification. In particular, when the Al alloy comprises Mg, the metal Si becomes an Mg-Si intermetallic compound, and thus the metal Si can be reduced together with Fe and Cu. However, this method is disadvantageous in that it is not suitable for large scale processing and causes a large amount of Al loss.

In the case of industrial large production, the most preferable method of removing metal Si is the said method in which the heat processing after rolling is performed at the temperature below 577 degreeC which is the co-crystallization temperature of Si-Al. Specifically, solution heat treatment of aluminum is performed and filtered to obtain an ingot. Then, isothermal heating is performed at about 550 degreeC, and when temperature falls to about 400 degreeC, rolling is performed, heat processing is performed, and cold rolling is performed. Here, when the temperature of the heat treatment is low, the formation of α-AlFeSi is impossible, and when the temperature is 577 ° C. or more, separation that causes metal Si occurs. Therefore, the range of 500 degreeC-570 degreeC is preferable, and, as for heat processing temperature, the range of 520 degreeC-560 degreeC is more preferable. In this way, the metal Si is removed from the Al material, and the anode oxidation is performed on the Al substrate including only the precipitated particles that can be anodized, whereby the dielectric breakdown start point can be eliminated, and the insulating properties can be improved.

It was confirmed that no Si peak was observed above the noise level during X-ray diffraction measurement of the surface of the Al substrate, and the Al substrate was a surface analysis apparatus in which SEM (scanning electron microscope) and EPMA (electron probe microanalyzer) were combined. Metal Si precipitated particle | grains which are not contained are determined by observing the surface or the cross section of this. When the precipitated particles are observed in the SEM image, characteristic X-rays are detected from the portion of the precipitated particles only for Si or only for Si and Al, which can determine that the precipitated particles are metal Si. When only Si and Al are detected, the reason for determining that the precipitated particles are metal Si is because there is no compound composed only of Si and Al. At this time, the characteristic X-rays of Al to be detected are characteristic X-rays of the Al substrate because the size of the precipitated particles is less than the spatial resolution that can be detected by the EPMA.

When adjusting the surface of the sample observed by using an abrasive containing Si such as SiO ₂ or SiC in the anode oxidation process, the abrasive may be embedded in the soft Al crystal structure. There is a possibility that this abrasive is incorrectly viewed as precipitated particles. For example, when the X-ray detection method of EPMA which cannot detect oxygen or carbon is EDS (energy dispersing type), this abrasive may be judged as metal Si. Therefore, when the Al substrate polished by the above method is analyzed by EDS, the Al substrate is immersed in a NaOH solution to dissolve the Al surface, and then washed and observed. By dissolving the Al surface, the embedded abrasive is separated and removed. As described in the above-mentioned document (edited by Japan Institute of Light Metal), it is known that metal Si does not dissolve in NaOH solution. In addition, when Al surface melt | dissolves as mentioned above, metal Si particle protrudes from the surface of an Al base material. Thus, an advantageous effect is obtained in which the metal Si particles can be distinguished more clearly during SEM observation.

In addition, a method other than the surface analysis of the Al substrate and X-ray diffraction measurement may be used to determine whether the metal Si particles are included or not. An example of such a method is a method in which an Al substrate is dissolved in a NaOH solution, an undissolved precipitate is recovered, and subjected to chemical analysis or X-ray diffraction analysis. However, as mentioned above, the definition of "metal Si particles are not included" refers to the extent that cannot be observed by the observation by EPMA based on Al and the X-ray diffraction measurement. In addition, the allowable range of the metal Si particles corresponding to the "range that can substantially solve the problem of the present invention" is observed by X-ray diffraction and X-ray diffraction measurement in terms of the definition of "not included" Is the same as the range in which metal Si cannot be observed.

As described above, the Al substrate of the first embodiment is characterized in that the precipitated particles contain only the precipitated particles 15 which are materials that can be anodized by anode oxidation.

The AAO substrate 2 (metal substrate having an insulating layer) manufactured using the Al substrate has a low leakage current in the insulating layer without any further processing since the Al substrate does not contain precipitated particles of an anodized material. And high withstand voltage can be realized. Therefore, the first embodiment can be manufactured by a simple process, and a metal substrate having an insulating layer having heat resistance during semiconductor processing, excellent voltage resistance and small leakage current can be obtained.

The thickness of the Al substrate 10 may be appropriately selected within the range of 50 to 5000 µm used as the metal substrate having the insulating layer 2. In manufacturing the metal substrate 2 having the insulating layer, the thickness of the Al substrate 1 is reduced due to anode oxidation and cleaning and polishing before the anode oxidation. Therefore, when selecting the thickness of the Al substrate, it is necessary to consider the reduced thickness.

Anode oxidation can be carried out by anode oxidation by immersing an Al substrate 1 functioning as a cathode and an anode in an electrolyte solution and applying a voltage between the anode and the cathode. In addition, as needed before the anode oxidation, the surface of the Al substrate 1 is subjected to cleaning treatment and polishing / smoothing treatment. Carbon or Al is used as the cathode. The electrolyte is not particularly limited, and preferred examples thereof include sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzene sulfonic acid; An acidic electrolyte solution containing at least one acid selected from amidosulfonic acid and the like. The conditions for anode oxidation are not particularly limited depending on the electrolyte used. The conditions were in the range of 1 to 80 mass% of electrolyte concentration, in the range of liquid temperature of 5 to 70 ° C, in the range of current density of 0.005 to 0.60 A / cm ^{2, in} the range of voltage of 1 to 200 V, and in the range of electrolytic time of 3 to 500 minutes. It is good to set it. As the electrolyte, sulfuric acid, phosphoric acid, oxalic acid or a mixture thereof is preferable. When these acids are used as an electrolyte, the range of the electrolyte concentration of 4-30 mass%, the range of the liquid temperature of 10-30 degreeC, the range of the current density of 0.002-0.30 A / cm <^2> , and the range of voltage 20-100V are preferable.

When the Al substrate 1 is anodized, an oxidation reaction proceeds from the surface 1s in a substantially vertical direction to form the anode film 11 and the non-anode oxide portion 10. When the acidic electrolyte solution is used, a plurality of fine columnar bodies 14 having a regular hexagonal shape in plan view are arranged without gaps in the anode film 11, and the fine pores in the center of each fine columnar body 14 are formed. 12) is formed, and the bottom surface of the fine pores 12 is rounded. At the bottom of the fine columnar body 14, a barrier layer 14b (usually in the range of 0.02 to 0.1 mu m in thickness) is formed. Instead of the acidic electrolyte solution, a dense anodized film can be obtained in place of the anodized film in which the porous fine columnar bodies 14 are arranged by performing an electrolytic treatment using a neutral electrolyte solution such as boric acid. In addition, in order to increase the thickness of the barrier layer 14b, a pore peeling method in which electrolytic treatment is performed with a neutral electrolyte after forming the porous anodized membrane 11 with an acid-based electrolyte can be used (H. Takahashi and S. Nagayama, "Pore-Filling of Porous Anodic Oxide Films on Aluminum", Journal of the Metal Finishing Society of Japan, Vol. 27, pp. 338-343, 1976).

The thickness of the anode film 11 is not particularly limited and needs to be made of a thickness that ensures surface hardness that can prevent damage due to mechanical impact during insulation and handling. However, if the thickness is too thick, there is a problem of solubility in some cases. For this reason, preferable thickness is the range of 0.5-50 micrometers. The thickness of the anode film 11 may be controllable by constant current electrolysis, constant voltage electrolysis and electrolysis time. The thickness of the Al substrate 1 is reduced due to the cleaning and polishing of the anode oxidation and the anode oxidation. Therefore, when selecting the thickness of the Al substrate, it is necessary to consider the reduced amount of thickness.

The AAO substrate 2 (metal substrate having an insulating layer) has good adhesion between the metal layer (non-anode portion) 10 and the insulator layer (anode film) 11. Therefore, as shown in FIG. 3B, the anode film 11 needs to be formed as an insulating layer on one surface of the Al substrate 1. However, there is a difference in the coefficient of thermal expansion of the non-anodeized portion 10 and the anodized film 11, so that if a problem occurs during the manufacturing step of the semiconductor device, the anodized film 11 is formed on both surfaces of the Al substrate. Is formed as an insulating layer. As a method of anodizing both surfaces of the Al substrate 1, there are a method of applying an insulating material to one surface and anodizing both surfaces by one surface and anodizing both surfaces simultaneously.

[Semiconductor Device]

Referring to the drawings, a structure of a semiconductor device according to a second embodiment of the present invention is described. Here, the semiconductor element of 2nd Embodiment is a photoelectric change element whose semiconductor is a photoelectric conversion semiconductor. 5 is a schematic cross-sectional view showing the photoelectric conversion element 3 according to the second embodiment of the present invention.

The photoelectric conversion element 3 includes a lower electrode (backside electrode) 20, a photoelectric conversion semiconductor 30, a buffer layer 40, and the like on the AAO substrate (metal substrate having an insulating layer) 2 of the first embodiment. It is an element formed by laminating | stacking the upper electrode (transparent electrode) 50. As shown in FIG. The lower electrode, photoelectric conversion layer and upper electrode of the photoelectric conversion element C are formed on an anodized film functioning as an insulating layer. The photoelectric conversion semiconductor is hereinafter referred to as the "photoelectric conversion layer".

A first groove 61 penetrating only the lower electrode 20 to the photoelectric conversion element 3, a second groove 62 and a photoelectric change layer 30 penetrating the photoelectric conversion layer 30 and the buffer layer 40, A third groove 63 penetrating the buffer layer 40 and the upper electrode 50 is formed.

In the above structure, a structure in which the first to third grooves 61 to 63 separate the elements into a plurality of elements C is obtained. Further, a structure is obtained in which the upper electrode 50 fills the second groove 62 and the upper electrode 50 of the predetermined element C is connected in series to the lower electrode 20 of the adjacent element C.

[Photoelectric conversion layer]

The photoelectric conversion layer 30 is a layer that generates a current by light absorption. Although the main component of the said photoelectric conversion layer is not specifically limited, It is preferable that it is a compound semiconductor which has at least 1 type of chalcopite structure. Moreover, it is preferable that the main component of the said semiconductor is at least 1 sort (s) of compound semiconductor containing group Ib element, group IIIb element, and group VIb element.

In addition, since these devices have high light absorption and exhibit high photoelectric conversion efficiency, the main component of the semiconductor, which is at least one compound semiconductor, is at least one group Ib element selected from the group consisting of Cu and Ag, Al, Ga And at least one group IIIb element selected from the group consisting of S, Se, and Te, at least one group IIIb element selected from the group consisting of In.

Examples of the compound semiconductor are CuAlS ₂ , CuGaS ₂ , CuInS ₂ , CuAlSe ₂ , CuGaSe ₂ , CuInSe ₂ (CIS), A ₉ AlS ₂ , AgGaS ₂ , AgInS ₂ , AgAlSe ₂ , AgGaSe ₂ , AgInSe ₂ , AgAlTe ₂ , AgGaTe ₂ , AgInTe ₂ , Cu (In _{1 - x} Ga _x ) Se ₂ (CIGS), Cu (In _{1 - x} Al _x ) Se ₂ , Cu (In _{1 - x} Ga _x ) (S, Se) ₂ , Ag (In _1-x Ga _x ) Se ₂ , and Ag (In _{1 - x} Ga _x ) (S, Se) ₂ .

It is preferable that the photoelectric change layer 30 include Cu (In _{1 - x} Ga _x ) Se ₂ (CIGS), which is CuInSe ₂ (CIS) and / or CuInSe _{2 in} which Ga is present as a solid solute. CIS and CIGS are semiconductors having a chalcopide crystal structure and have been reported to exhibit high light absorption and high photoelectric conversion efficiency. In addition, there is little deterioration in efficiency due to light irradiation, and they are excellent in durability.

The photoelectric conversion layer 30 contains impurities for obtaining a desired semiconductor conductivity. The impurities may be included in the photoelectric conversion layer 30 by diffusion and / or active doping from adjacent layers. In the photoelectric conversion layer 30, the constituent elements and / or impurities in the I-III-VI semiconductor may have concentration distribution, and a plurality of layer regions having different semiconductor properties such as n-type, p-type, and i-type It may be included. For example, in the CIGS system, the width and carrier mobility of the band gap can be controlled by the amount of Ga having a distribution in the thickness direction, and the photoelectric conversion efficiency can be well designed. The photoelectric conversion layer 30 may include one or two or more semiconductors in addition to the I-III-VI semiconductor. Examples of semiconductors other than the I-III-VI semiconductors include semiconductors of group IVb elements such as Si (group IV semiconductors), group IIIb elements such as GaAs and semiconductors of group Vb (groups III-V) and CdTe. Semiconductors of group IIb elements and group VIb elements (group II-VI semiconductors) are included. As long as the semiconductor characteristics are not adversely affected, components other than impurities may be included in the photoelectric conversion layer 30 to obtain a desired semiconductor conductivity. The amount of the group I-III-VI semiconductor included in the photoelectric change layer 30 is not particularly limited, and is preferably 75% by weight or more, more preferably 95% by weight or more, and most preferably 99% by weight or more.

Known methods for forming a CIGS layer include: 1) multi-factor simultaneous deposition (JR Tuttle et.al, "The Performance of Cu (In, Ga) Se ₂ -Based Solar Cells in Conventional and Concentrator Applications", Mat. Res. Soc. Symp. Proc. Vol. 426, pp. 143-151, 1996; and H. Miyazaki et al., "Growth of high-quality CuGaSe2 thin films using ionized Ga precursor", phys.Stat.sol. (A), Vol 203, pp. 2603-2608, 2006), 2) selenization method (Nakada et al., "CuInSe2-based solar cells by Se-vapor selenization from Se-containing precursors", Solar Energy Materials and Solar Cells, Vol. 35, pp. 209-214, 1994; and T. Nakada et al., "THIN FILMS OF CuInSe ₂ PRODUCED BY THERMAL ANNEALING OF MULTILAYERS WITH ULTRA-THIN STACKED ELEMENTAL LAYERS", Proceedings of the 10th European Photovoltaic Solar Energy Conference (EU PVSEC), pp. 887-890, 1991), 3) sputtering method (JH Ermer et al., "CdS / CuInSe ₂ JUNCTIONS FABRICATED BY DC MAGNETRON SPUTTERING OF Cu ₂ Se AND In ₂ Se ₃ ", Proceedings of the 18th IEEE Photovoltaic Spe cialists Conference, pp. 1655-1658, 1985; and T. Nakada et al., "Polycrystalline CuInSe2 Thin Films for Solar Cells by Three-Source Magnetron Sputtering", Japanese Journal of Applied Physics, Vol. 32, Part 2, No. 8B, pp. L1169-L1172, 1993); 4) Hybrid sputtering method (T. Nakada et al., "Microstructural Characterization for Sputter-Deposited CuInSe ₂ Films and Photovoltaic Devices", Japanese Journal of Applied Physics, Vol. 34, Part 1, No. 9A, pp. 4715-4721 , 1995), and 5) Mechanochemical processing (T. Wada et al., "Fabrication of Cu (In, Ga) Se2 thin films by a combination of mechanochemical and screen-printing / sintering processes", Physica status solidi (a), Vol. 203, No. 11, pp. 2593-2597, 2006). Other methods of forming the CIGS layer include screen printing, near-sublimation, MOCVD, and spray methods. For example, the particulate film containing the Group Ib element, Group IIIb element, and Group VIb element is formed on the substrate by screen printing or spraying, and then pyrolysis is performed (in this case, the pyrolysis treatment is performed in the Group VIb element atmosphere. Crystals of the desired composition are obtained (Japanese Unexamined Patent Publication No. 9 (1997) -074065, 9 (1997) -074213, etc.). 6 is a graph showing the relationship between the lattice constant and the band gap in a main I-III-VI compound semiconductor. Various band gaps can be obtained by changing the composition ratio. When protons with a larger energy than the bandgap enter the semiconductor, energy exceeding the bandgap becomes heat loss. Theoretical calculations performed on the combination of the spectrum and bandgap of the solar light reveal that the photoelectric conversion rate is maximized within the range of 1.4 eV to 1.5 eV. In order to increase the photoelectric conversion efficiency, a band gap having a high conversion efficiency can be obtained by increasing the band gap. The band gap may be, for example, to increase the Ga concentration of Cu (In, Ga) Se ₂ (CIGS), to increase the Al concentration of Cu (In, Al) Se ₂ or to Cu (In, Ga) (S, Se) can be increased by increasing the S concentration of ₂ .

(Electrode and buffer layer)

The lower electrode 20 (backside electrode) and the upper electrode 50 (transparent electrode) are both made of a conductive material. The upper electrode 50 on the light incident side needs to be light transmissive.

Mo may be used as the material of the lower electrode 20. It is preferable that the thickness of the lower electrode 20 is 100 nm or more, and it is more preferable that it is the range of 0.45-1.0 micrometer. The method of forming the lower electrode 20 is not particularly limited. Examples of forming the lower electrode 20 include gaseous growth methods such as electron beam deposition and sputtering. ZnO, ITO (indium tin oxide), SnO _2, or a combination thereof is preferable as the main component of the upper electrode 50. The upper electrode 50 may have a single layer structure or a laminated structure such as a two layer structure. It is preferable that CdS, ZnS, Zn0, ZnMg0, ZnS (O, OH) or a combination thereof be the material of the buffer layer 40.

Semiconductor devices having a Mo bottom electrode, a CIGS photoelectric conversion layer, a CdS buffer layer and a ZnO top electrode are examples of preferred combinations of compositions.

It is reported that alkali metal elements (element Na) in a soda lime glass substrate are dispersed in a CIGS film and improve the photoelectric conversion efficiency of the photoelectric conversion element using the soda lime glass substrate. In the present invention, it is preferable to disperse the alkali metal in the GIGS film. Examples of a method of dispersing an alkali metal element in the CIGS film include a method of forming a layer containing the alkali metal element on the Mo lower electrode by vapor deposition or sputtering (for example, Japanese Unexamined Patent Publication No. 8 (1996) ) -222750), a method of forming an alkali layer made of Na ₂ S or the like by immersion on a Mo lower electrode (see, for example, WO03 / 069684), and In, Cu and After the precursor containing a Ga metal element is formed, the method of attaching the aqueous solution containing sodium molybdate, for example to the precursor is included.

In another preferred configuration, the lower electrode 20 is preferably a layer containing one or two alkali metal compounds such as Na ₂ S, Na ₂ Se, NaCl, NaF, and sodium molybdate salt.

The conductivity type of the photoelectric conversion layer 30-upper electrode 50 is not specifically limited. Usually, the photoelectric conversion layer 30 includes a p layer, the buffer layer 40 includes an n layer (n-CdS, etc.), and the upper electrode 50 includes an n layer (n-ZnO, etc.), or an i layer and an n layer. It is a structure (lamination structure etc. which consist of an i-ZnO layer and an n-ZnO layer). In this conductivity type, it is considered that a p-n junction or a p-I-n junction is formed between the photoelectric conversion layer 30 and the upper electrode 50. In addition, when the buffer layer 40 formed of CdS is provided on the photoelectric conversion layer 30, Cd diffuses, an n layer is formed on the surface of the photoelectric conversion layer 30, and a pn junction is formed in the photoelectric conversion layer. I think. In addition, i layer is formed as a white layer in the photoelectric conversion layer 30, and it is thought that p-I-junction is formed in a photoelectric conversion layer.

(Other layers)

The photoelectric conversion element 3 can be provided with a layer other than the above as needed. For example, an adhesive layer (buffer layer) to increase adhesion between layers between the metal substrate 10 having the insulating layer and the lower electrode 20 and / or between the lower electrode 20 and the photoelectric conversion layer 30. This can be installed. In addition, an alkali barrier layer for suppressing diffusion of alkali ions may be provided between the metal substrate 2 having the insulating layer and the lower electrode 20. Japanese Unexamined Patent Publication No. 8 (1996) -222750 can be referred to for the alkali barrier layer.

The photoelectric conversion element 3 can be used suitably for a solar cell. The solar cell 4 can be constructed by closely adhering a cover glass, a protective film, or the like onto the photoelectric conversion element 3. However, the semiconductor element of the present invention is not limited to the photoelectric conversion element. It is applicable to mesa-type semiconductor elements other than the planar semiconductor element described above. In addition, the present invention can be applied to a vertical semiconductor device and a horizontal semiconductor device. As a specific example, the present invention can be applied to a flexible transistor or the like.

As described above, the semiconductor element 3 and the solar cell of the present invention use the metal substrate 2 having the insulating layer 2 of the present invention. Therefore, the same effect as that shown by the metal substrate 2 with the insulating layer 2 is exhibited, and it is a semiconductor element which can utilize the original photoelectric conversion characteristic to the maximum, and is excellent in durability.

(Example)

Hereinafter, examples and comparative examples of the semiconductor device according to the present invention are described.

(Evaluation standard)

<Identification of Metal Internal Compound 1-X-ray Diffraction>

Identification of the metal internal compound was carried out with RINT-2000, an X-ray diffractometer manufactured by Rigaku, using a CuKα beam, and measured. Higher peak intensity indicates a larger mass of precipitates. The conditions and physical properties of the examples and the comparative examples are shown in Table 1. In Table 1, "-" indicates that no specific diffraction peak is detected, only noise level intensity is detected. Counts per second (Cps) was used as the unit of measurement, and an intensity of about 150 cps or less was designed as the noise level intensity.

<Identification of Compound 2 in Metals-SEM and EPMA>

The identification of metal internal compounds was carried out by a surface analysis apparatus combining SEM (Ultra 55, Zeiss) and EPMA (Thermo, NORAN system (Energy Dispersion Type)). The acceleration voltage was 10 kV and the spatial resolution was about 0.5 μm. Weight percent was used as the unit of measure. In Table 1, "-" indicates that the metal intermolecular compound was not measured.

(Example 1)

The solution was prepared using aluminum having a purity of 99.99% or more as used in JIS1N99, and solution heat treatment and filtration were performed to produce an ingot 500 mm thick and 1200 mm wide by the DC casting method. The surface of the ingot was milled to an average thickness of 10 mm by surface miller. Subsequently, isothermal heating was performed at 550 ° C. for about 5 hours. When the temperature was lowered to 400 ° C., the ingot was rolled with a hot rolling mill to form a plate with a thickness of 2.7 mm. In addition, heat treatment was performed at 500 ° C. for 1 hour with an annealing apparatus, and the rolled plate was finished by cold rolling using a mirror finished roll to a thickness of 0.24 mm.

The surface of the Al material was ultrasonically cleaned with ethanol and electropolished with a mixed solvent of acetic acid and perchloric acid. Subsequently, the Al plate was subjected to constant voltage electrolysis at a voltage of 40 V in a 0.5 g / L oxalic acid solution to form an anode film having a thickness of 10 μm on the surface of the Al plate. No precipitate was found in the Al substrate, and no disturbance was present in the porous structure of the anodized film.

(Example 2)

The solution was prepared using aluminum with a purity of at least 99.99% and 4% by weight Mg as used in JIS1N99. An Al material was prepared in the same manner as in Example 1 except for the addition of Mg.

When X-ray diffraction measurement was performed on the Al material, the peak showed 37.5 °, and it was confirmed that fine precipitates having a size smaller than 1 μm exist in the Al substrate, and were also identified as Al ₃ Mg ₂ by EPMA. .

Subsequently, an anode film having a thickness of 10 µm was formed in the same manner as in Example 1.

As shown in FIG. 7, there was a disturbance in the porous structure of the anodized membrane. Mg was detected together with Al and oxygen from these parts by EPMA measurements. Therefore, these portions were judged to be the positions where Al ₃ Mg ₂ was anodized. However, the part where Al ₃ Mg ₂ is present was not an empty space, but was a confused porous structure, and the confused porous structure was continuous with the Al substrate.

(Example 3)

The solution was prepared using aluminum having a purity of 99.99% or more as used in JIS1N99, and solution heat treatment and filtration were performed to prepare an ingot 500 mm thick and 1200 mm wide by the DC casting method. Next, an aluminum material having a thickness of 0.24 mm was produced in the same manner as in Example 1 except that the heat treatment was performed at a temperature of 520 ° C.

When X-ray diffraction measurement was performed on the Al material, it was confirmed that the peak represented 42.0 ° and the Al material contained α-AlFeSi. It was confirmed that fine precipitates having a maximum size of 3 μm exist in the Al substrate, and Al ₃ Fe, Al ₆ Fe, and AlFeSi were identified by EPMA.

Subsequently, an anode film having a thickness of 10 μm was formed in the same manner as in Example 1. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe, Al ₆ Fe and AlFeSi were detected together with oxygen. Therefore, these portions were judged to be the positions where Al ₃ Fe, Al ₆ Fe, and α-AlFeSi were anodized.

(Example 4)

The solution was prepared using aluminum having a purity of 99.99% or more as used in JIS1000, and solution heat treatment and filtration were performed to produce an ingot 500 mm thick and 1200 mm wide by the DC casting method. Next, an aluminum material having a thickness of 0.24 mm was produced in the same manner as in Example 1 except that the heat treatment was performed at a temperature of 520 ° C.

When X-ray diffraction measurements were made on the Al material, the peaks showed 42.0 °, 18.0 ° and 42.0 °, and it was confirmed that the Al material contained Al ₃ Fe, Al ₆ Fe and α-AlFeSi. It was confirmed that fine precipitates having a maximum size of 3 μm exist in the Al substrate, and Al ₃ Fe, Al ₆ Fe, and AlFeSi were identified by EPMA.

Subsequently, an anode film having a thickness of 10 μm was formed in the same manner as in Example 1. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe, Al ₆ Fe and AlFeSi were detected together with oxygen. Therefore, these portions were judged to be the positions where Al ₃ Fe, Al ₆ Fe, and α-AlFeSi were anodized.

(Example 5)

An Al material was produced in the same manner as in Example 4 except that the heat treatment was performed at 560 ° C. for 1 hour by the annealing apparatus.

When X-ray diffraction measurements were made on the Al material, the peaks showed 24.1 °, 18.0 ° and 42.0 °, and it was confirmed that the Al material contained Al ₃ Fe, Al ₆ Fe and α-AlFeSi. It was confirmed that fine precipitates having a maximum size of 3 μm exist in the Al substrate, and Al ₃ Fe, Al ₆ Fe, and AlFeSi were identified by EPMA.

Subsequently, an anode film having a thickness of 10 μm was formed in the same manner as in Example 1. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe, Al ₆ Fe and AlFeSi were detected together with oxygen. Therefore, these portions were judged to be the positions where Al ₃ Fe, Al ₆ Fe, and α-AlFeSi were anodized.

(Example 6)

An aluminum material was prepared in the same manner as in Example 1 except that a solution was prepared by using aluminum having a purity of 99.99% or more and Fe by 1% by weight as used in JIS1000.

When X-ray diffraction measurements were made on the Al material, the peaks showed 24.1 °, 18.0 ° and 42.0 °, and it was confirmed that the Al material contained Al ₃ Fe, Al ₆ Fe and α-AlFeSi. It was confirmed that fine precipitates having a maximum size of 3 μm exist in the Al substrate, and Al ₃ Fe, Al ₆ Fe, and AlFeSi were identified by EPMA.

Subsequently, an anode film having a thickness of 10 μm was formed in the same manner as in Example 1. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe, Al ₆ Fe and AlFeSi were detected together with oxygen. Therefore, these portions were judged to be the positions where Al ₃ Fe, Al ₆ Fe, and α-AlFeSi were anodized.

(Example 7)

Al material was prepared in the same manner as in Example 6. The surface of the Al material was ultrasonically cleaned and electropolished with a mixed solvent of acetic acid and perchloric acid. Subsequently, the Al plate was subjected to constant voltage electrolysis at 13 V in a 1.73 mol / L sulfuric acid solution to form an anode film having a thickness of 10 μm on the surface of the Al plate. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe, Al ₆ Fe and AlFeSi were detected together with oxygen. Therefore, these portions were judged to be the positions where Al ₃ Fe, Al ₆ Fe, and α-AlFeSi were anodized.

(Comparative Example 1)

A solution was prepared using aluminum having a purity of 99.8% or more as used in JIS1N1080, and solution heat treatment and filtration were performed to produce an ingot 500 mm thick and 1200 mm wide by the DC casting method. An Al material having a thickness of 0.24 mm was produced in the same manner as in Example 1 except that the heat treatment was performed at a temperature of 400 ° C.

When X-ray diffraction measurements were made on the Al material, the peaks showed 24.1 ° and 28.4 °, and it was confirmed that the Al material contained Al ₃ Fe and metal Si. It was confirmed that fine precipitates having a maximum size of 3 µm exist in the Al substrate, and Al ₆ Fe and Si were identified by EPMA.

Subsequently, an anode film having a thickness of 10 μm was formed in the same manner as in Example 1. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe was anodized, but the metal Si was not anodized and remained in the Al material as the metal Si.

(Comparative Example 2)

An Al material was prepared in the same manner as in Comparative Example 1 except that the solution was prepared using aluminum having a purity of 99.0% or more as used in JIS1100.

When X-ray diffraction measurements were made on the Al material, the peaks showed 24.1 °, 18.0 ° and 28.4 °, and it was confirmed that the Al material contained Al ₃ Fe, Al ₆ Fe and metal Si. It was confirmed that fine precipitates having a maximum size of 3 µm exist in the Al substrate, and Al ₃ Fe, Al ₆ Fe, and metal Si were identified by EPMA.

Subsequently, an anode film having a thickness of 10 μm was formed in the same manner as in Example 1. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe and Al ₆ Fe were anodized, but the metal Si was not anodized and remained in the Al material as the metal Si.

(Comparative Example 3)

An Al material was prepared in the same manner as in Comparative Example 1 except that the solution was prepared using aluminum having a purity of 99.0% or more as used in JIS 1100, and the heat treatment was performed at a temperature of 600 ° C.

When X-ray diffraction measurements are made on the Al material, the peaks represent 24.1 °, 18.0 °, 42.0 ° and 28.4 °, the Al material comprising Al ₃ Fe, Al ₆ Fe, α-AlFeSi and metal Si It was confirmed. It was confirmed that fine precipitates having a maximum size of 3 µm exist in the Al substrate, and Al ₃ Fe, Al ₆ Fe, α-AlFeSi, and metal Si were identified by EPMA.

Subsequently, an anode film having a thickness of 10 μm was formed in the same manner as in Example 1. As a result of the EPMA measurement performed on the cross section of the anodized film, Al ₃ Fe, Al ₆ Fe and α-AlFeSi were anodized, but metal Si was not anodized and remained in the Al material as metal Si.

(Comparative Example 4)

An Al material was prepared in the same manner as in Comparative Example 2. An anodized film having a thickness of 10 µm was then formed in the same manner as in Example 7. As a result of the EPMA measurement performed on the cross section of the anode film, Al ₃ Fe and Al ₆ Fe were anodized, but metal Si was not anodized and remained in the Al material as metal Si.

(Measurement of Insulation Characteristics)

The dielectric breakdown voltage was measured about each board | substrate of the Example and the comparative example which use Al layer as an anode. Insulation property measurement was performed by forming the electrode formed from Au which is 0.2 micrometer in thickness, and 3.5 mm in diameter by mask vapor deposition, applying a constant voltage to this Au electrode, and observing the time change of the leakage current. The current was measured for 60 seconds at 1 second intervals. Here, the value obtained by dividing the leakage current by the Au electrode area (9.6 mm ² ) is the leakage current density.

In addition, the inventors have found that the anode film exhibits very high insulation characteristics when the voltage is applied to the A1 layer as the anode as compared with the case where a voltage is applied to the Al layer as the cathode (see Japanese Patent Application No. 2009-093536). ). The details of the reason are unclear at present, but it is presumed that the barrier layer grows as the defects in the barrier layer self repair. In other words, when a voltage is applied so that the Al base material 1 becomes an anode, an electric field is concentrated in a portion in the electrically weak barrier layer, and an anode oxidation phenomenon is given priority in the vicinity of these weak portions. As a result, self repair of defects is prioritized, and it is estimated that barrier-free barrier layers grow over time.

(evaluation)

8A is a diagram showing the overcurrent characteristic of Example 1. FIG. In the overcurrent characteristic of FIG. 8A, a large leakage current is not confirmed, and dielectric breakdown does not occur even when a voltage of 100OV is applied. When the voltage 200V was applied for 60 seconds, the leakage current density was 1.0 x 10 ^-7 A / cm ² .

8B is a diagram illustrating the overcurrent characteristic of Example 2. FIG. As in Example 1, in the overcurrent characteristic of Fig. 8B, no large leakage current was confirmed, and no dielectric breakdown occurred even when a voltage of 100OV was applied. When the voltage 200V was applied for 60 seconds, the leakage current density was 7.5x10 ^-8 A / cm ² . In Example 2, the precipitated particles were only Mg aluminized compounds. Therefore, it was demonstrated that the Al plate having only the anodized precipitated particles of the present invention had an effect equivalent to that of the high purity Al plate.

Similarly, no dielectric breakdown occurred in any of Examples 3-7. When the voltage 200V is applied for 60 seconds for each of Examples 3-7, the leakage current densities are 2.2 × 10 ^-8 A / cm ² , 6.6 × 10 ^-7 A / cm ² , 7.2 × 10 ^-7 A /, respectively. cm ² , 8.5 × 10 ⁻⁷ A / cm ^2, and 1.5 × 10 ⁻⁶ A / cm ² .

8C is a graph showing the overcurrent characteristic of Comparative Example 1. FIG. In the overcurrent characteristic of Fig. 8, a large variation in leakage current was confirmed, but insulation breakdown occurred 15 seconds after the start of the application of the voltage of 600V. It is presumed that the cause of the dielectric breakdown is poor insulation due to a large defect due to the presence of metal Si (non-anodized precipitated particles) in the barrier layer, and the barrier layer is not grown because the metal Si does not have a self-repairing Al element. As a result, it is considered that leakage current characteristics and withstand voltages are greatly reduced as compared with the examples, and sufficient insulation cannot be obtained. When the voltage 200V was applied for 60 seconds, the leakage current density was 5.1 × 10 ^-6 A / cm ² .

Likewise, no dielectric breakdown of Comparative Examples 2-4 occurred at 330V, 420V, and 360V, respectively. Since the amount of the metal Si content was large, it was estimated that the dielectric breakdown occurred in Comparative Examples 2 to 4 to which a voltage lower than that of Comparative Example 1 was applied. When a voltage of 200 V was applied to each of Comparative Examples 2-4 for 60 seconds, the leakage current densities were 1.6 × 10 ^-5 A / cm ² , 9.6 × 10 ^-6 A / cm ^2, and 3.3 × 10 ^-5 A /, respectively. cm ² .

As described above, the Al material of Examples 1-7 substantially contains no metal Si. When the anode film was formed using this Al material, it was confirmed that the dielectric breakdown voltage was 1000 V or more. On the other hand, although the extent differs, the said Al material of the comparative examples 1-4 contains metal Si. When an anode film was formed using such an Al material, it was confirmed that the metal Si was not anodized, remained in the Al material as the metal Si, and dielectric breakdown occurred upon application of a voltage of less than 1000V. Therefore, the breakdown start point of the non-anode metal Si particles could be confirmed.

In addition, in Example 2-7, although the precipitated particle exists, when it was the precipitated particle | grains which can be anodized, there was no problem regarding insulation characteristics. Preferably, the Al substrate contains only materials that can be anodized and is substantially free of metal Si that cannot be anodized.

Hereinafter, the conditions and the characteristic of an Example and a comparative example are shown in Table 1.

Claims (11)

As Al substrate used in the method of forming the metal substrate which has the insulating layer for semiconductor elements by performing anode oxidation on at least one surface:
An Al substrate comprising only precipitated particles of a material that can be anodized by anode oxidation as precipitated particles in an Al matrix. The method of claim 1,
The anode material is an Al substrate, characterized in that the intermetallic compound containing one of Al and Mg. The method according to claim 1 or 2,
An Al substrate, wherein the metal Si is substantially not included as precipitated particles in the Al substrate. An anode film is formed on at least one surface of the Al substrate by performing anode oxidation on at least one surface of the Al substrate according to any one of claims 1 to 3. A metal substrate having an insulating layer. A metal substrate having an insulating layer according to claim 4;
A semiconductor layer provided on the metal substrate; And
And at least one pair of electrodes for applying a voltage to the semiconductor layer. The method of claim 5, wherein
And the semiconductor is a photoelectric conversion element having a photoelectric conversion function in which the semiconductor layer generates current by absorbing light. The method according to claim 6,
The main component of the semiconductor layer is a semiconductor device, characterized in that the compound semiconductor having at least one chalcopite structure. The method of claim 7, wherein
A semiconductor device according to claim 1, wherein the main component of the semiconductor is at least one compound semiconductor containing a group Ib element, a group IIIb element, and a group VIb element. The method of claim 8,
The main component of the semiconductor is at least one group Ib element selected from the group consisting of Cu and Ag;
At least one group IIIb element selected from the group consisting of Al, Ga and In; And
A semiconductor device comprising at least one compound semiconductor comprising at least one group VIb element selected from the group consisting of S, Se, and Te. The solar cell provided with the semiconductor element of any one of Claims 6-9. Preparing an Al substrate;
Melting the Al substrate to obtain an Al ingot;
Isothermally heating the Al ingot at a temperature below the co-crystallization temperature of Si-Al;
Cooling the Al ingot to a temperature at which rolling is possible;
Rolling the Al ingot;
Heat-treating the rolled Al at a temperature below the co-crystallization temperature;
Cold rolling the heat-treated Al substrate to obtain an Al substrate; And
And anode-oxidizing at least one surface of the surface of the Al substrate with respect to the Al substrate.

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